1. Field of Invention
The invention relates to a method of flue stream heating fine-grained, thermally inert substances, in order to produce a briquetting material.
2. Description of Prior Art
German Pat. No. 1 571 711 discloses a method of producing fuel briquettes, in which thermally inert substances, such as for example coking duff, lean fine coal, ore, limestone, sand, and raw phosphate, are used, and treated with coking coal which softens at a high temperature, as a binding agent.
This hot briquetting method is known in the technical literature as the Ancit method. The state of the art is reproduced in the research Report T 82-144 of the Federal Ministry of Research and Technology of the Federal Republic of Germany.
According to the state of the art the mixing and briquetting temperature is about 500.degree. C. The charging components consist of, on the one hand, 72.+-.10% of fine-grained substances which do not soften below 800.degree. C., i.e. thermally inert substances, such as oil coke, coking duff (grit), pitch coke and/or fine-grained coal with less than 14% volatile constituents, sand, ores, metal oxides, metals, industrial dust, or mixtures of such substances, and, on the other hand, 18.+-.10% of coking coal. The components are heated in the flue stream. The carrier gas is produced in a combustion chamber arranged upstream of the flue stream reactor by as nearly as possible stoichiometric combustion of gaseous and/or liquid fuels. In the Ancit method the two components are introduced successively into the carrier gas, are heated, and are separated again from the carrier gas with the aid of cyclones.
The hot, inert substances at 550.degree. to 650.degree. C. (proportions of 72.+-.10%) are mixed with the coking coal heated to 200.degree. to 400.degree. C. (proportions of 18.+-.38%) and are partially degassed and briquetted, in particular at a temperature of 500.degree..+-.50.degree. C.
The heat requirement of the method is considerable and furthermore cannot be covered by process heat. This is due to two reasons, namely that caking of slags occurs in the first flue stream reactor and, in addition, the softening temperature is exceeded in the second cyclone. The latter circumstance has also made it impossible hitherto, when hot-briquetting low-ash, solid fuels, to cover more than 1/3 of the process heat by burning off in the flue stream cloud.